Probability

Indicator expectation

Converts a probability question into an expectation question, which linearity can then take apart.

\mathbb{E}[I_A] = \Pr(A)

Where

$I_A$: One when the event $A$ occurs, zero otherwise.

Sanity check. Only valid for a variable that takes the values 0 and 1 — no other two-point variable.

Where this is taught

Linearity of expectation · PROB · Expectation, variance and the big tricks